Voters in Alabama and Mississippi have their say on Tuesday in the next stage of the contest to select an opponent for President Barack Obama in November's general election.

Mr Romney, a relative moderate former Massachusetts governor, faces a battle against Newt Gingrich, a former House Speaker, who won the first two deep-southern votes in South Carolina and Georgia.

The multimillionaire former private equity boss, who turns 65 today, has striven to woo voters wary of the north-eastern liberal elite, even declaring himself an "unofficial Southerner" at a recent rally.

"Mornin' y'all, good to be with you," he joked awkwardly. Referring to the local breakfast of porridge-like ground corn, he added: "I got started right this morning with a biscuit and some cheesy grits. I'll tell you! Delicious."

Yet he later told an Alabama radio station that really he preferred Honey Nut Cheerios. "I try to eat some cold cereal at the end of the day," he said. "A full tummy and a long day puts me right to bed." Matt Murphy, an Alabama radio host, declared on Twitter that "no self-respecting Southerner should vote for Romney after what he said", later adding that it highlighted his "southern disconnect".

While Mr Romney's 17 wins give him more party delegates than his opponents combined, and he is likely to win the nomination, he has consistently struggled to enthuse the party's Right-wing "base".

Many southern evangelical Christians are also concerned by his Mormon faith, an issue that is rarely discussed publicly but which emerged last week during another interview.

"Do you, as a Mormon, believe America is the new promised land?" he was asked on the Rick and Bubba Show. "You're going to have to go talk to the Church and ask what they think about that," he replied.

Opinion polling in both southern states has been scant, but Mr Romney appears to hold narrow leads over Mr Gingrich. He also leads in Hawaii and American Samoa, which hold caucuses tomorrow. Rick Santorum, the evangelical Catholic who has split much of the anti-Romney support with Mr Gingrich, pledged yesterday to continue battling Mr Romney's lukewarm campaign.

"He has all the establishment behind him, has all this quote wind as his back, yet he can't close the deal," Mr Santorum told a television interview.

Mr Santorum won a landslide victory in the Kansas caucus over the weekend while Mr Romney was victorious in the US territories of Guam, the Northern Marianas and the Virgin Islands.